The present invention provides polycarbonates and copolycarbonates of reduced water uptake and improved flowability, processes for their preparation and their use for the production of particular products and the products obtainable therefrom. The invention furthermore provides new bisphenols and processes for their preparation and their use.
Aromatic polycarbonates belong to the group of industrial thermoplastics. They are distinguished by the combination of the technologically important properties of transparency, heat resistance and toughness.
To obtain high molecular weight polycarbonates by the phase boundary process, the alkali metal salts of bisphenols are reacted with phosgene in the two-phase mixture. The molecular weight may be controlled by the amount of monophenols, such as e.g. phenol or tert-butylphenol. Practically exclusively linear polymers are formed in these reactions. This may be demonstrated by end group analysis. Branched polycarbonates are also obtained in this reaction by the controlled use of so-called branching agents, as a rule polyhydroxylated compounds.
For the preparation of polycarbonates by the phase boundary process, reference may be made by way of example to H. Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, vol. 9, Interscience Publishers, New York 1964 p. 33 et seq. and to Polymer Reviews, vol. 10, “Condensation Polymers by Interfacial and Solution Methods”, Paul W. Morgan, Interscience Publishers, New York 1965, chap. VIII, p. 325.
For the preparation of polycarbonates by the melt transesterification process, the bisphenols are reacted with diaryl carbonates, usually diphenyl carbonate, in the presence of catalysts, such as alkali metal salts or ammonium or phosphonium compounds, in the melt.
The melt transesterification process is described, for example, in the Encyclopedia of Polymer Science, vol. 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, vol. 9, John Wiley and Sons, Inc. (1964) and DE-C 10 31 512.
However, the polycarbonates and copolycarbonates already described in the prior art are unsatisfactory due to their water uptake and the limited dimensional stability thereby caused, or have the disadvantage that when used as data carrier materials they may be of limited or non-optimum suitability at reading wavelengths in the blue or blue-green range.